Phul Kumari, 25, stands with her child in front of a window in a village community center in in India's northern state of Uttar Pradesh in 2011. From a poor rural community in India's Jharkhand state, Kumari was trafficked to Uttar Pradesh to become a bride.

Nine 7-Eleven store owners and managers who authorities say ran a “modern-day plantation system,” employing dozens of immigrant workers at New York and Virginia convenience stores, were just one thread in a vast human trafficking and forced labor web that stretches around the world and into American homes.

Investigators filed indictments earlier this week against the eight men and one woman who were accused of hiding dozens of illegal immigrants from Pakistan and the Philippines at a string of convenience stores in two states.

The nine defendants arrested by investigators allegedly employed more than 50 illegal immigrants at ten 7-Eleven franchises in New York and four more in Virginia, using stolen identities to cover up their illicit activities, authorities said on Monday.

But while these alleged victims were discovered, Secretary of State John Kerry said on Wednesday that millions of victims of human trafficking slip past law enforcement every year as he released the State Department's 2013 Trafficking in Persons report.

"When we think of the scale of modern-day slavery, literally tens of millions who live in exploitation, this whole effort can seem daunting, but it's the right effort," Kerry said. "There are countless voiceless people, countless nameless people except to their families or perhaps a phony name by which they are being exploited, who look to us for their freedom."

Federal agents and police raid more than a dozen convenience stores in New York and Virginia, and arrest owners and managers for allegedly forcing foreign workers to work very long hours, for very little pay in their stores. Jay Gray reports.

Only about 40,000 victims of human trafficking have been identified in the past year, the report said, based on information obtained from governments around the world. The estimated number of men, women, and children who are trafficked at any one time worldwide may reach as high as 27 million, according to the report.

“Because reporting is uneven, we can’t say for certain how many victims of trafficking are identified each year,” said Ambassador Luis C. deBaca, director of the Office to Monitor and Combat Trafficking in Persons, in an introduction to the report.

“That means we’re bringing to light only a mere fraction of those who are exploited in modern slavery,” deBaca said. “That number, and the millions who remain unidentified, are the numbers that deserve our focus.”

The report designated 21 countries as Tier Three, signifying that they make no significant effort to meet minimum standards of compliance set by the Trafficking Victims Protection Act, a 2000 law that allows for the prevention and prosecution of human trafficking.

After the release of the State Department's 2013 Trafficking in Persons report Secretary of State John Kerry talks about the importance of American leadership in combatting human trafficking.

Yet the number of traffickers convicted by the Department of Justice fell over the past year, the report said, recording 138 traffickers convicted in 2012, according to the report. A year earlier, 152 convictions were obtained by the Justice Department in trafficking cases, the report said.

As many as 100,000 U.S. children may be victims of domestic human trafficking, according to estimates cited by a 2013 Congressional Research Service report. The tally of victims brought into the U.S. by traffickers each year might be as high as 17,500 people, according to the report.

In another domestic case announced by investigators this week, a woman with cognitive disabilities and her young daughter beaten and threatened in their Ohio home for more than two years, authorities said. Three people were arrested for holding the two victims captive against their will since May 2011, according to the U.S. Attorney for Northern Ohio.

Jessica L. Hunt, 31, and Daniel J. Brown, 33, and Jordie L. Callahan, 26, allegedly held the two victims captive and kept them under surveillance using a video monitor in an Ashland, Ohio apartment, according to an affidavit filed on June 17 in Ohio’s Northern District Court.

Police were alerted to the alleged abuses when the adult victim was arrested in October of 2012 for shoplifting a candy bar, and asked to be taken to jail rather than back to the apartment, according to the affidavit.

The victims in Ohio were forced to shop and clean for their captors, as well as care for their pit bulls and pet reptiles, according to the affidavit. They were denied food, beaten, and threatened with firearms, as well as snakes including a poisonous coral snake, and 130-pound Burmese python, and a ball python, according to the affidavit.

"We are yet again reminded that modern-day slavery exists all around us," said Steven M. Dettelbach, United States Attorney for the Northern District of Ohio. "One of our nation's core values is freedom, yet this woman and her child were denied freedom for two years.”

The chief executive of the Polaris Project, a non-governmental organization that works to prevent human trafficking, said the report brought attention to the “appallingly high rate” of global human trafficking in a statement.

“The average American should understand that human trafficking is much larger and more prevalent than most people realize, and they may come across human trafficking in their daily lives,” Polaris Project CEO Bradley Myles told NBC News in an email. “Hundreds of thousands of vulnerable women, men and children right here in the U.S. are lured or forced into commercial sex or to provide labor against their will.”

President Barack Obama has named human trafficking as a priority of his administration, and last year signed an executive order tightening safeguards and adding protections against use of trafficked labor by the government and federal subcontractors. In April, the White House hosted a forum on its efforts to crack down on human trafficking.

“But for all the progress that we’ve made, the bitter truth is that trafficking also goes on right here, in the United States,” Obama said in a speech on human trafficking in September 2012. “It’s the migrant worker unable to pay off the debt to his trafficker. The man, lured here with the promise of a job, his documents then taken, and forced to work endless hours in a kitchen. The teenage girl, beaten, forced to walk the streets. This should not be happening in the United States of America.”